The present invention relates to a cutting insert for chip forming machining of preferably metallic work pieces, said cutting insert having at least one cutting edge created by the transition between an upper face and a side face of the cutting insert, said upper face constituting a rake face or contact face between the cutting insert and the chip formed during machining and said side face constitutes a flank, and that the rake face comprises a chip upsetting face arranged adjacent to the cutting edge and a curved chip breaking face arranged adjacent to the chip upsetting face.
During use of conventional cutting inserts of this type the formed chip contacts the cutting insert in the chip upsetting face, said chip is furnished with its characteristic lamination and that said chip emits a part of its heat to the cutting insert. Then the chip is bent and formed to an easily handled breakable chip along the chip breaking face. The lamination and chip forming is thus carried out in two timely separated steps.
The present invention intends to deform the chip in three steps in quick running in order to decrease the cutting force.